The purpose of this Center proposal is to conduct transdisciplinary research, training, and outreach on obesity and cancer in youth, family, and young adults. The proposed Center will address questions about the etiology, prevention, and treatment of obesity in youth and families, and explore biological pathways that may link obesity to cancer. The center proposal includes three specific research projects. Project 1 is a multifactorial, cross-sectional, and prospective observational study examining predictors of obesity development in adolescents, including sociocultural factors, family factors, environmental factors, and individual factors. Project 2 is a study evaluating family-base, weight-gain prevention intervention that particularly emphasizes intervention on environmental contributors to weight gain. Project 3 is a study of the effects of physical activity on estrogen metabolism, oxidative stress, and DNA repair mechanisms in young women. The three R01 grants will be supported by one core, a Data Services and Analysis Core. The proposal also includes a career development component, substantial funding for developmental projects, and a dissemination/translation component. The overall goals are to advance transdisciplinary science in the advancement of understanding of obesity, youth, family, and cancer;to support the career development of new investigators in the field;and to disseminate scientific knowledge about the topic to broader audiences.